Semiconductor integrated circuit device

ABSTRACT

A semiconductor integratd circuit device includes fuse elements formed on an element isolation insulating film, and an insulating film, an interlayer insulating film and a silicon nitride film successively formed over the fuse elements. An opening region extends through the silicon nitride film into the interlayer insulating film above the fuse elements, and openings formed in the interlayer insulating film are positioned on both sides of middle portions of the fuse elements. The openings facilitate blowing off of the insulating film during laser cutting of the fuse elements, reducing physical damage to the element isolation insulating film under the fuse elements.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor integrated circuitdevice including a fuse element.

2. Description of the Related Art

In a semiconductor integrated circuit device manufacturing process thereis a method of setting elements for circuit configuration by cutting afuse element formed of polysilicon, metal, and the like by using, forexample, a laser after a wafer manufacturing process is finished. Withthe use of this method, a resistance value can be corrected to obtaindesired characteristics after electrical characteristics of thesemiconductor device are measured. The method is thus effectiveparticularly for a semiconductor device that places emphasis on itsanalog characteristics.

A conventional semiconductor integrated circuit device is illustrated inFIG. 5 and FIG. 6. FIG. 5 is a plan view of fuse elements 103, and FIG.6 is a sectional view taken along the line A-A? of FIG. 5. Asillustrated in FIG. 6, the fuse elements 103 are formed on an elementisolation insulating film 102, and are formed of a polycrystalline Sifilm doped with impurities, which is the same conductive material asthat of a gate electrode (not shown) of a MOS transistor.

Further, an opening region 108 that is used for cutting middle portionsof the fuse elements 103 with a laser is formed above the fuse elements103. The opening region 108 is hitherto formed by selectively etching aninterlayer insulating film 105 formed for the purpose of metallamination and a silicon nitride film 106 formed for the purpose ofprotecting an internal element from moisture coming in from the outsiderespectively using a mask. At that time, the insulating film on the fuseelement 103 should be adjusted to have a thickness in a certain range,taking into consideration variations that occur in a process such asdeposition or etching of the insulating film and variations in laserintensity during cutting of the fuse elements 103. The reason is that,if a fuse element 103 is exposed, the fuse element 103 expands under theinfluence of the moisture and a crack may develop along an interfacebetween the exposed fuse element 103 and a fuse element 103 covered withthe insulating film, which may adversely affect the internal element.Meanwhile, when the fuse element 103 is cut with a laser, it isnecessary to blow off the insulating film simultaneously with the fuseelement 103. At this time, if the insulating film on the fuse element103 is too thick, the insulating film on the fuse element 103 is notblown off so easily, and thermal energy for the blowing off istransferred to the element isolation insulating film 102 under the fuseelement 103 to physically damage the element isolation insulating film102, which results in generation of a crack. If a residue of thescattered fuse element 103 enters the crack, the residue and a siliconsubstrate 101 may be electrically connected to each other, leading toabnormal electrical characteristics.

In order to deal with the problem described above, various devices foralleviating damage to a base film have been made that includesmeasurement and strict control of a film thickness of a fuse opening,increasing the thickness of the insulating film under the fuse element103 with respect to other element isolating film thicknesses, and layinga damage block material on the base film (for example, Japanese PatentApplication Laid-open No. 2010-056557).

However, when the thickness of the insulating film 102 under the fuseelement 103 is increased with respect to other element isolating filmthicknesses or a material for blocking damage is laid on the base film,there is apprehension that the level difference between the siliconsubstrate 101 and the element isolation insulating film 102 may beincreased. Therefore, the aspect ratio of a contact of an element formedon the silicon substrate 101 becomes very high, and there is apossibility that the contact is not formed or electrical connection ismade that exhibits an unusually high contact resistance value.Meanwhile, even if the contact of the element formed on the siliconsubstrate 101 is electrically connected, a contact to the fuse element103 may pierce the film of the fuse element 103 to cause a qualityabnormality.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a semiconductorintegrated circuit device that enables stable cutting of a fuse withoutthe apprehension described above and without causing abnormal qualitywhen the fuse is cut.

In order to solve the above-mentioned problem, the following means istaken in one embodiment of the present invention.

First, provided is a semiconductor integrated circuit device, including:

a semiconductor substrate;

an element isolation insulating film formed on a surface of thesemiconductor substrate;

a plurality of fuse elements, each of which is formed of firstpolycrystalline silicon, and are arranged on the element isolationinsulating film at intervals;

an insulating film formed on the plurality of fuse elements;

an interlayer insulating film formed on the insulating film;

a silicon nitride film formed on the interlayer insulating film;

an opening region formed above the plurality of fuse elements, theopening region being formed by removing part of the silicon nitride filmand part of the interlayer insulating film; and

concaves formed by removing a remaining portion of the interlayerinsulating film under the opening region, the concaves being formed inthe vicinity of both sides of each of fuse middle portions of theplurality of fuse elements at regular intervals.

Further, in the semiconductor integrated circuit device, the concavesformed in the vicinity of both sides of each of the fuse middle portionsof the plurality of fuse elements at regular intervals have slit-likeshapes.

Further, in the semiconductor integrated circuit device, the concavesformed in the vicinity of both sides of each of the fuse middle portionsof the plurality of fuse elements at regular intervals have small squareshapes.

Further, in the semiconductor integrated circuit device, the number ofthe concaves formed in the vicinity of both sides of each of the fusemiddle portions of the plurality of fuse elements at regular intervalsis one between adjacent fuse elements.

According to the present invention, even when the thickness of theinsulating film on the fuse elements is set to be large, the slit-likeconcaves are formed in the vicinity of both sides of each of the fusemiddle portions of the fuse elements at regular intervals, and thus, theinsulating film can be blown off more easily when cut with a laser. As aresult, physical damage to the element isolation insulating film underthe fuse elements can be reduced to prevent electrical connection withthe semiconductor substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of a semiconductor integrated circuitdevice according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view of the semiconductor integratedcircuit device taken along the line A-A′ of FIG. 1.

FIG. 3 is a schematic plan view of a semiconductor integrated circuitdevice according to a second embodiment of the present invention.

FIG. 4 is a schematic plan view of a semiconductor integrated circuitdevice according to a third embodiment of the present invention.

FIG. 5 is a schematic plan view of a related-art semiconductorintegrated circuit device.

FIG. 6 is a schematic sectional view of the related-art semiconductorintegrated circuit device taken along the line A-A′ of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention are described below with referenceto the attached drawings.

FIG. 1 is a schematic plan view of a semiconductor integrated circuitdevice according to a first embodiment of the present invention. FIG. 2is a schematic sectional view of the semiconductor integrated circuitdevice according to the first embodiment of the present invention takenalong the line A-A? of FIG. 1. First, a structure of a fuse region inplan view is described with reference to FIG. 1. A plurality of fuseelements 103 are arranged in spaced-apart side-by-side relationship on asurface of an element isolation insulating film formed on a siliconsemiconductor substrate. A fuse middle portion of the fuse element 103is thinner than both end portions thereof so as to be easily cut with alaser. Slit-like openings such as concaves 201 are formed in thevicinity of both sides of each of fuse middle portions of the fuseelements 103 at regular intervals. Further, an opening region 108 inwhich a polyimide 107, a silicon nitride film 106 serving as aprotective film, and an interlayer insulating film 105 are etchedpartway for the purpose of cutting with a laser is formed above themiddle portions of the plurality of fuse elements 103 as shown in FIG.2. Therefore, the concaves 201 are formed so as to be exposed at thebottom of the fuse opening region 108. The present invention has afeature in that the slit-like concaves 201 are formed so as to beadjacent to the fuse elements 103, respectively, in the interlayerinsulating film 105 above the fuse element 103. In this embodiment, theslit-like concaves 201 are rectangular in plan view.

FIG. 2 is a schematic sectional view of the semiconductor device takenalong the line A-A′ of FIG. 1. The element isolation insulating film 102at a thickness of from 4,000 Å to 7,000 Å, for example, is formed on thesilicon semiconductor substrate 101. The fuse elements 103 on theelement isolation insulating film 102 are formed of a polycrystalline Sifilm doped with impurities that is the same layer and the sameconductive material as those of a gate electrode (not shown) of a MOStransistor. The fuse elements 103 have a thickness of from about 2,000 Åto about 4,000 Å. An insulating film 104 for insulating an elementformed on the silicon substrate 101 and metal wiring from each other,for example, a BPSG film is formed on the fuse elements 103, and themetal wiring and the interlayer insulating film 105 for the purpose ofmetal wiring lamination are formed on the insulating film 104. Further,the silicon nitride film 106 is laminated for the purpose of protectingan internal element from moisture coming in from the outside. Finally,the polyimide 107 for alleviating stress on a package is laminated, andafter that, the opening region 108 is formed in the polyimide 107. Then,part of the silicon nitride film 106 and part of the interlayerinsulating film 105 are etched subsequently with the remaining polyimide107 itself being used as a mask, thereby forming the opening region 108.Then, another mask is used for patterning and the rest of the interlayerinsulating film 105 is etched to form the slit-like concaves 201: Atthis time, etching selectivity between the interlayer insulating film105 and the insulating film 104 thereunder is small, and thus, it isdifficult to stop the etching at an interface therebetween. Theinsulating film 104 may be etched to some extent.

With such a structure, the slit-like concaves 201 are on both sides ofeach of the fuse elements 103, and adjacent concaves 201 of adjacentfuse elements 103 are spaced apart and separated from one another. Thusthe interlayer insulating film 105 is separated along the fuse elements103, which facilitates blowoff of the interlayer insulating film 105when laser light is radiated even when the interlayer insulating film105 above the fuse elements 103 is thick. Therefore, even when theinterlayer insulating film 105 above the fuse elements 103 is thick, itis not necessary to increase the output of the laser, and physicaldamage to the element isolation insulating film 102 under the fuseelements 103 can be reduced. In this embodiment, the concaves arerectangular in plan view, but it goes without saying that the concavesmay be polygonal or oval.

FIG. 3 is a schematic plan view of a semiconductor integrated circuitdevice according to a second embodiment of the present invention. Whilethe concaves (openings) 201 are rectangular slits in the firstembodiment, in the second embodiment, the concaves (openings) 201 are aplurality of small square concaves 201. A plurality of square concaves201 are on both sides of a fuse element 301, and thus, the interlayerinsulating film 105 is partly separated along the fuse elements 103,which facilitates blowoff of the interlayer insulating film 105 whenlaser light is radiated. Note that, the small concaves may berectangular or circular.

FIG. 4 is a schematic plan view of a semiconductor integrated circuitdevice according to a third embodiment of the present invention. Whiletwo lines of concaves 201 are formed between adjacent fuse elements 103in FIG. 1 and in FIG. 3, as illustrated in FIG. 4, one line of concave(openings) 201 may be formed between adjacent fuse elements 103. In thiscase, the concaves 201 can have an increased width (width in a directionof intervals of adjacent fuse elements 103), which is advantageous inthat fuse cutting is further facilitated and in that the possibility isfurther reduced that the interlayer insulating film 105 damages theelement isolation insulating film 102 under the adjacent fuse elements103 when blown off by radiated laser light.

In the above description, part of the polyimide 107, part of the siliconnitride film 106, and part of the interlayer insulating film 105 areetched in succession using the first mask to form the opening region108, and then, the rest of the interlayer insulating film 105 is etchedusing the second mask to form the concaves 201. Alternatively, thepolyimide 107 and the silicon nitride film 106 may be etched insuccession using the first mask to form the opening region 108, andthen, the interlayer insulating film 105 may be etched using the secondmask to form the concaves 201. Forming of the concaves 201 as in thepresent invention facilitates blowoff of the interlayer insulating film105, and thus, such a process can be set. Further, there is a case inwhich the polyimide 107 is not used, but it goes without saying that thepresent invention can be completely similarly applied to such a case.

As described above, even when the thickness of the insulating film 104on the fuse elements 103 is set to be large, the concaves 201 are formedin the interlayer insulating film 105 in the vicinity of both sides ofeach of the fuse middle portions of the fuse elements 103 at regularintervals, and thus, the insulating film can be blown off more easilywhen cut with a laser. As a result, physical damage to the elementisolation insulating film 102 under the fuse elements 103 can be reducedto prevent electrical connection with the silicon substrate 101.

What is claimed is:
 1. A semiconductor integrated circuit device,comprising: a semiconductor substrate; an element isolation insulatingfilm disposed on a surface of the semiconductor substrate; fuse elementsdisposed in spaced-apart side-by-side relationship on the elementisolation insulating film, each fuse element having two opposite endportions interconnected by a middle portion; an insulating film disposedon the fuse elements; an interlayer insulating film disposed on theinsulating film; a silicon nitride film disposed on the interlayerinsulating film; an opening region extending through the silicon nitridefilm into the interlayer insulating film at a location above the fuseelements; and openings formed in the interlayer insulating film at abottom of the opening region, the openings being positioned on bothsides of the middle portions of the fuse elements, adjacent openings ofadjacent fuse elements being spaced apart and separated from oneanother, and plural openings being positioned on each side of the middleportions of the fuse elements.
 2. A semiconductor integrated circuitdevice according to claim 1; wherein the openings have a square shape.